川南二叠系煤层气井防腐防垢工艺

川南筠连煤层气属深层煤层气，含煤10余层，近几年出现大范围井下管柱腐蚀结垢，造成检泵停产，严重影响开发进程。通过对12组垢样的XRD分析发现，垢样是罕见的含CaCO₃、FeCO₃及SiO₂的多种无机矿物混合体，常规Ca/Mg盐的缓蚀阻垢剂并不适用，需探索新的防腐防垢工艺。以激光粒度检测法、失重法、静态阻垢法、绝迹稀释法对6种缓蚀阻垢剂(EDTMPS、HEDP、ATMP、EDTMPA，PESA、PASP)和2种杀菌剂(1227、戊二醛)进行分散、缓蚀、阻垢及杀菌效果评价。结果显示，戊二醛杀菌效果较好，30 mg/L时可完全杀菌，对颗粒粒径无显著影响，EDTMPS与PESA缓蚀阻垢效果较好，复配比为1∶1，90 mg/L时阻垢率、缓蚀率分别达84.56%、92.34%，可有效降低颗粒粒径。最终确定防腐防垢配方为:45 mg/L有机磷类阻垢剂EDTMPS+45 mg/L聚合物类阻垢剂PESA+30 mg/L戊二醛杀菌剂，用连续泵注设备由环空注入井下，3~6 d时采出水Ca2+质量浓度由200 mg/L升至380 mg/L，Fe2+质量浓度由14 mg/L降至8 mg/L，细菌数接近0个/mL。长期跟踪发现，因腐蚀、结垢造成的检泵周期分别由665 d、681 d延长至749 d、880 d。以EDTMPS、PESA与戊二醛为主的缓蚀阻垢配方可有效缓解本区井下管柱的腐蚀结垢。

Corrosion and scale control technology used in the Permian CBM wells of southern Sichuan Basin

The coalbed methane in Junlian of southern Sichuan Basin is deep coalbed methane and there are over 10 coal seams. In recent years, corrosion and scaling of downhole string occurs extensively, which leads to pump inspection and off production and seriously impacts the development process. In this paper, 12 groups of scale samples were analyzed by means of XRD. It is shown that scale samples are the rare mixture of multiple inorganic minerals containing CaCO₃, FeCO₃ and SiO₂, so the conventional corrosion and scale inhibitor of Ca/Mg salt is not applicable and it is necessary to explore a new corrosion and scale control technology. Then, the dispersion, corrosion control, scale inhibition and bactericidal effects of 6 kinds of corrosion and scale inhibitors (EDTMPS, HEDP, ATMP, EDTMPA, PESA and PASP) and 2 kinds of bactericidal agents (1 227 and glutaraldehyde) were evaluated by means of laser grain size detection method, weight loss method, static scale inhibition method and vanishing dilution method. It is shown that glutaraldehyde has better bactericidal effect and it can kill the bacteria completely at 30 mg/L without influencing the grain size obviously. EDTMPS and PESA have better corrosion and scale inhibition effect. At the mixing ratio of 1∶1 and the concentration of 90 mg/L, scale inhibition rate and corrosion inhibition rate are up to 84.56% and 92.34% respectively and the grain size is decreased effectively. The eventually determined corrosion and scale control formula is 45 mg/L organic phosphorus scale inhibitor EDTMPS+45 mg/L polymer scale inhibitor PESA+30 mg/L glutaraldehyde bactericidal agent. It is injected through the annulus by using the uninterrupted pumping unit, and 3-6 d later, the mass concentration of Ca2+ in the produced water rises from 200 mg/L to 380 mg/L, that of Fe2+ drops from 14 mg/L to 8 mg/L and the number of bacteria is nearly 0. Long-term follow up shows that the pump inspection cycle caused by corrosion and scaling is extended from 665 d and 681 d to 749 d and 880 d, respectively. In conclusion, the corrosion and scale inhibitor dominated by EDTMPS, PESA and glutaraldehyde can effectively alleviate the corrosion and scaling of downhole string in this block.